Systems and Methods for Fly-Height Control Using Servo Data

Abstract

Various embodiments of the present invention provide systems and methods for determining changes in fly-height. For example, various embodiments of the present invention provide storage devices that include a storage medium having servo data thereon. A read / write head assembly is disposed in relation to the storage medium. A servo based fly-height adjustment circuit receives the servo data via the read / write head assembly, and calculates a first harmonics ratio based on the received data and compares the first harmonics ratio with a second harmonics ratio to determine an error in the distance between the read / write head assembly and the storage medium.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]The present application claims priority to (is a non-provisional of) U.S. Pat. App. No. 61 / 013,658 entitled “A Resynchronization Approach for Harmonic Estimation Using Half-Rate Preamble”, and filed Dec. 14, 2007 by Mathew et al. The entirety of the aforementioned application is incorporated herein by reference for all purposes.BACKGROUND OF THE INVENTION[0002]The present inventions are related to systems and methods for accessing a storage medium, and more particularly to systems and methods for determining the location of a read / write head assembly in relation to a storage medium.[0003]Writing information to a magnetic storage medium includes generating a magnetic field in close proximity to the storage medium to be written. This may be done using a read / write head assembly as are commonly known in the art, and is highly dependent on properly positioning the read / write head assembly in relation to a magnetic storage medium. The distance...

AI Technical Summary

Benefits of technology

[0009]Other embodiments of the present invention provide methods for identifying a distance error based on servo data. Such methods include, providing a first harmonic ratio corresponding to a known position; providing a storage medium that includes servo data; accessing the servo data from the storage medium using a read / write head assembly; calculating a second harmonic ratio based on the servo data; and comparing the first harmonic ratio with the second harmonic ratio to determine a distance error. In some instances of the aforementioned embodiments, the first harmonic ratio is calculated during an initialization phase and corresponds to a know fly-height. In some instances of the aforementioned embodiments, the methods further include adjusting a distance from the read / write head assembly to the storage medium such that the distance error is reduced.

Problems solved by technology

While the approach provides a reasonable static estimate of fly-height, it does not provide an indication of any change in fly-height occurring during standard operational periods.

As such, the approaches do not provide an ability to adjust for changes occurring during the operation of the disk.

The de-convolution requires matrix inversion, and it becomes very difficult to implement the matrix inversion as the matrix size increases, which it does as the truncation length of the channel correlation is relaxed.

It is also difficult to use this approach to obtain the CBD variation in continuous fashion, as it works on a block by block basis.

Such an approach is able to continuously monitor fly-height during normal operational periods, however, the accuracy of the approach is significantly diminished due to PVT-induced variations in the signal / circuits.

More importantly, none of the aforementioned approaches facilitate fly-height monitoring and control during normal write operations.

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